1. Field of the Invention
This invention relates to automatic validation checks applied to traffic monitoring equipment including traffic speed detection equipment. The invention is, however, in principle applicable to any traffic data collection equipment subject to what will be said herein below. An area of primary application which is envisaged, for-example, is traffic monitoring equipment based on a cable, cables and/or detector pads, magnetic loop detectors or others such as optical systems or pneumatic tube systems extending across a road or other surface and providing electrical signals for timing/counting purposes.
As is known such electrical signals can have one or more of several physical origins including piezo-electric effects either resistive and/or generative piezo-electric effects, capacitive effects and tribo-electric effects, for example. These signals are used to start and stop time measurements in order to calculate for example vehicle speed, axle distance, tyre contact length etc., and count or weigh axles of vehicles passing over these sensors. The validation checks or security checks are to be provided to enhance the reliability, accuracy and convenience of operating such equipment. This can have favourable legal implications when the equipment is used for law enforcement. Generally less reliance is therefore placed on the operator of the equipment to ensure the integrity of the equipment and the security of the measurements it takes.
2. Prior Art
In the application of the existing art a number of sources of error could exist which have as yet not been satisfactorily dealt with. As a result the existing equipment is subject to possible error from these causes. These include cable swopping errors (including incorrect sequence of signals), insufficient signal amplitudes, radio frequency interference or electromagnetic interference with the signals, spurious signals or signals of non-standard timing originating from damaged cables.
Thus there is a problem of improvement of measuring, for example, the speed of vehicles, on the basis that speed equals distance divided by time more, accurately and reliably by this invention. The improvement of accuracy lies within checking one or a combination of the factors which will be discussed below.